Connecting classification with phylogeny
Connecting classification with phylogeny
Using phylogeny to trace the relatives of birds
Each tree is a hypothesis about the most likely path of evolution based on the data available
- Critical innovations: Derived traits
- adaptive traits that define new taxa
- marked with ‘slashes’ on tree
- ‘shared derived character’ in book
- evolutionary novelties
- Shared ancestral traits: a trait that is found in the ancestor of a group and all of the derived taxa have the trait
- What makes a bird a bird?
Anatomy of a phylogenetic tree
How to draw phylogenies: branch shape and length
How to draw phylogenies: branch shape and length
Mapping traits on a phylogeny (review homology)
Convergent evolution in marine mammals (analogous traits)
How to use derived characters to infer phylogeny
How to use derived characters to infer phylogeny
- Parsimony = Simplest solution is the likely path of evolution
- A logical way to identify homologous and analogous traits
- Minimize the # of evolutionary changes needed to explain your character data
How to use derived characters to infer phylogeny
Whale Evolution: A Case History
- Phylogenetic trees based on morphology place whales outside of the artiodactyl group
- Atiodactyl: mammals - cows, deer and hippos
- hooves, even number of toes
- unusual pulley-shaped ankle bone
- Astragalus ankle bone is a shared derived trait for all artiodactyls
Whale Evolution: A Case History
- How do we determine evol’n relationships?
- morphology - presence/absence of weird ankle bone
- DNA sequences - shared gene families
- Depends on what data you have!
- poor fossil records made this tricky
- Molecular data suggests a closer relationship between whales and hippos…
Whale Evolution: Whales and Hippos share common ancestor
